I. We previously demonstrated that the toxins alpha-sarcin, ricin, Shiga toxin and Shiga-like toxin all inactivate protein synthesis in cells by attacking a highly conserved region near the 3'-end of 28S ribosomal RNA. We have now shown that microinjection of modified deoxyoligonucleotides, ribonucleotides and ribozymes complementary to the same region of 28S RNA also abolish protein synthesis. We have also demonstrated that certain nucleases are surprisingly effective at abolishing protein synthesis and that one of these nucleases selectively hydrolyzes tRNA, but not ribosomal or mRNAs, when injected into Xenopus oocytes. II. During early development Xenopus replicates its DNA nearly as fast as E. coli in log phase; perhaps indicating that oocytes may be an excellent source of DNA repair activity. We demonstrated pyrimidine dimer repair by microinjecting UV-irradiated plasmid DNA into oocytes or adding damaged DNA to an extract derived from oocytes. We have also studied DNA repair for alkylated and chemically modified DNA. We are also investigating DNA replication with our repair extract.